With more than $88 billion to his name, there isn’t much Warren Buffett couldn’t buy. Except, as the now 88-year-old CEO and chairman of Berkshire Hathaway is keenly aware, there is one thing his fortune won’t help him get more of: time.

“It’s the only thing you can’t buy. I mean, I can buy anything I want, basically, but I can’t buy time,” the “Oracle of Omaha” says in a 2017 conversation with his billionaire buddy Bill Gates, hosted by Charlie Rose.

Rose asks Gates what he has learned from Buffett. First, he learned that it’s “not necessarily a good idea to leave large sums to your children,” says the Microsoft co-founder. And then there was the little paper appointment book Buffett showed Gates.

“I also remember Warren showing me his calendar,” says Gates. Buffett hands his little book to Rose to examine. “There’s nothing on it,” says Rose, flipping through the book.